I'd prefer to see it expressed in simple X-Y terms, with X being the amount of extension measured at a 90 degree angle from the steering axis forward from the center of the steer tube to the center of the handlebar, and Y being the vertical deviation in millimeters from the center of the clamping area on the steer tube. Yes, that means that the actual angles and lengths with respect to the horizontal and vertical planes change a bit with changing steer tube angles, but that is no different than how it is today now, is it?